DC1434A - Demo Manual

DEMO CIRCUIT 1434
LT3071
QUICK START
GUIDE
LT3071
5A, Low Noise, Programmable Output, 85mV
Dropout Linear Regulator with Analog Margin
DESCRIPTION
Demonstration circuit 1434 is an adjustable 5A linear
regulator featuring LT3071. LT3071 is a low dropout
voltage, UltraFastTM transient response linear regulator. The device supplies up to 5A of output current
with a typical dropout voltage of 85mV. A 0.01µF reference bypass capacitor decreases output voltage
noise to 25µVRMS. The LT3071’s high bandwidth permits the use of low ESR ceramic capacitors.
Output voltage is digitally selectable in 50mV increments over a 0.8V to 1.8V range. An analog
margining function allows the user to adjust system output voltage over a continuous ±10% range.
To maintain proper performance and regulation,
the BIAS supply voltage must be higher than the
IN supply voltage. For a given VOUT, the BIAS voltage must satisfy the following conditions:
2.2 ≤ VBIAS ≤ 3.6V and VBIAS ≥ (1.25·VOUT+1V).
For VOUT ≤ 0.95V, the minimum bias voltage is limited to 2.2V.
Performance Summary (TA = 25oC)
PARAMETER
Minimum Input Voltage
Maximum Input Voltage
Minimum Bias Voltage
Maximum Bias Voltage
Output Voltage VOUT
Maximum Output Current
The IC incorporates a unique tracking function to
control buck regulator powering the LT3071’s input. This tracking function drives the buck regulator to maintain the LT3071’s input voltage to VOUT +
300mV, minimizing power dissipation. It has internal protection includes UVLO, reverse-current protection, precision current limiting with power foldback and thermal shutdown.
The LT3071 regulator is available in a thermally
enhanced 28-lead, 4mm×5mm QFN package.
The LT3071 datasheet gives a complete description of the part, operation and application
information. The datasheet must be read in conjunction with this quick start guide for demo circuit 1434.
Design files for this circuit board are available. Call the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
UltraFast is a trade mark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
CONDITION
VOUT=1.2V, IOUT = 5A
VOUT=1.2V
JP1=LOW, JP2=HIGH, JP3=HIGH
VIN -Vout < 0.5V
VALUE
1.32V
3V
2.5V
3.6V
1.2V ±1%
5A
QUICK START PROCEDURE
Demonstration circuit 1434 is easy to set up to
evaluate the performance of the LT3071. Refer
to Figure 1 for proper measurement equipment
setup and follow the procedure below:
1.
Place JP5 on the ON position.
1
LT3071
2.
Use JP1, JP2, JP3 and MAGRA
voltage to set the desired output voltage.
3.
With power off, connect the input
power supply to Vin and GND.
4.
Connect the bias voltage to Vbias
and GND.
5.
Turn on the power at the input and
the bias pin.
7.
Once the proper output voltage is established, adjust the load within the operating
range and observe the output voltage
regulation, efficiency and other parameters.
NOTE.
Make sure that the power dissipation is lim-
ited below the thermal limit.
NOTE. Make sure that the input voltage does not exceed 3V
and the bias voltage is within its limit.
6.
Check for the proper output voltage.
NOTE. If there is no output, temporarily disconnect the load to
make sure that the load is not set too high.
Figure 1. Proper Measurement Equipment Setup
2
*
*
GND
VIN
1.1V - 3V
PWRGD
VIOC
VBIAS
E6
E5
E3
E2
E1
JP5
C6
1000pF
CIN1
+
220uF
10V
(Opt)
VIN
R1
49.9K
1%
OFF
3
POWER
1
ON
2
SEE QUICK START GUIDE
FOR VBIAS RANGE
0.01uF
C3
CIN2
47uF
10V
1206
U1
LT3071EUFD
8
7
6
5
3
2
1
IN
IN
IN
IN
27
V BIA S
25
VO2
24
VO1
VO0
OUT
OUT
OUT
OUT
SE NS E
M A RGA
IM O N
JP2
VO1
23
4
3
2
1
VBIAS
4
9
10 11 12 13 14 20 26 29
GN DG NDGN DG NDGN DG NDGN DG NDGN DG ND
REF /BY P
P WRGD
V IO C
EN
28
2.2uF
VBIAS
VBIAS
4
FLOAT
C1
3
JP1
2
LOW
1
HIGH
VO2
15
16
17
18
19
22
C4
10uF
10V
0805
JP3
VO0
1K
R2
4
FLOAT
21
3
2
1
LOW
HIGH
VBIAS
FLOAT
LOW
HIGH
C7
4.7uF
10V
0805
C8
2.2uF
10V
0805
C5
10uF
10V
0805
E8
E7
E4
E9
GND
VOUT
0.8 - 1.8V @ 5A
MARGA
0V - 1.2V
2V @ 5A
FULL SCALE
LT3071
3
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